Tibial component of an artificial knee joint

ABSTRACT

A tibial component of an artificial knee joint is provided which cooperates with a femoral component to allow pivoting rotation of the artificial knee joint in either a clockwise or counterclockwise direction. The tibial component includes a plate with a tapered dovetail rib thereon which allows an insert to be removably secured thereto to act as a meniscal structure for the tibial component. The insert has a proximal surface with left and right wells therein that include valleys to guide rotation of one condylar leg of a femoral component while holding a second condylar leg of the femoral component within the other one of the wells, allowing pivoting rotation in either direction. A nesting of the insert into a portion of the plate minimizes an overall height of the tibial component and minimizing tibial bone resection, while providing a greater resistance to shear forces upon the knee joint.

CROSS-REFERENCE TO RELATED APPLICATIONS

The following patent application is being filed in coordination withanother patent application having a very similar disclosure and relatedto other portions of a common artificial knee joint. This othercorresponding application is entitled “FEMORAL COMPONENT OF ANARTIFICIAL KNEE JOINT,” has the same inventor, was filed on the same dayand has Ser. No. 12/148,363.

FIELD OF THE INVENTION

The following invention relates to surgical implants placed within aknee of a patient to function as an artificial knee joint. Moreparticularly, this invention relates to artificial knee joints whichinclude a femoral component, a tibial component and a patellar componentwhich exhibit a simplified femoral component, femoral component sizing,bone preparation procedures, tibial component meniscal insert low wearcharacteristics and dual direction knee pivoting rotation functiontherein.

BACKGROUND OF THE INVENTION

Human knee joints endure exceptional loads and a wide variety of loadingscenarios throughout the life of an individual. While the human kneejoint is capable of supporting most of these typical loads under normalconditions for the life of the individual, in certain circumstances thehuman knee joint suffers degraded performance. For instance, injury canoccur to the knee causing the knee to not fully repair itself, or notbeing fully repairable through medical intervention, such that itbecomes beneficial to replace the knee joint with an artificial kneejoint. In other circumstances, degenerative disease can act on thenatural knee joint to degrade its performance in an irreversiblefashion, such that replacement of the natural knee joint with anartificial knee joint is indicated.

Artificial knee joints are well known in the literature and have comeinto widespread use. In general, such artificial knee joints include afemoral component, a tibial component and a patellar component. Thedistal end of the femur is surgically prepared to have the distal endthereof have a contour matching an internal box surface of the femoralcomponent. The femoral component is then attached to the distal end ofthe femur. Similarly, the proximal end of the tibia is prepared,typically by cutting a flat proximal surface on the proximal end of thetibia, and the tibial component is attached to this proximal end of thetibia. Muscles and ligaments surrounding the knee are disturbed aslittle as possible so that they can continue to function in the samemanner that they do with a natural knee joint. Proximal surfaces of thetibial component and distal surfaces of the femoral component abut eachother and are designed to facilitate articulation relative to each otherin the same way that the distal end of a natural femur articulatesrelative to the proximal end of a natural tibia. Typically, an insert ofmaterials somewhat more flexible and resilient than metal is attached toa proximal end of the tibial component, with other portions of thetibial component formed of a more rigid material, such as titanium orcobalt chrome. This insert in some ways duplicates the function of anatural meniscus within a natural knee joint, and helps to minimizefriction in the articulation of the femoral component relative to thetibial component.

Numerous drawbacks have been noted with prior art artificial knee jointsand for which this invention strives to provide a significant andbeneficial improvement. For instance, artificial knee joints are knownfor being somewhat complex to implant, and most particularly the femoralcomponent. In particular, the distal end of the femur must beextensively shaped to properly mate with facets on the internal box faceof the femoral component.

In the prior art, the surgeon must make numerous very precise cuts onthe distal end of the femur and these cuts vary based on the particulargeometry of the facets on the internal box face of the femoralcomponent. Because different human bodies have different sizes, variousdifferent femoral components having different sizes must be consideredbefore selecting the particular femoral component. Typically, a cuttingjig or other specialized tool must be selected that matches with thefemoral component selected so that the cuts are properly made.

As a result, the surgeon, manufacturer or an associated health carefacility must maintain an extensive inventory of femoral cutting jigsfor potential use in an artificial knee joint surgical procedure. Suchextensive inventory of cutting jigs is expensive to maintain, requiresadditional space within the surgery room or nearby, and presents thegreater possibility of problems during or after surgery. Furthermore, anincrease of such cutting jigs is more difficult to clean and sterilizewhich increases the potential for infection, in turn resulting in a lessthan fully desirable outcome. U.S. Pat. Nos. 5,925,049 and 5,749,876both describe a femoral cutting instrument sizer that allows a singletool to be used for a set of femoral components of different sizeshowever both devices are cumbersome and complicated to use. Accordingly,a need exists for an artificial knee joint which has a femoral componentwhich is one of a set of femoral components of different sizes whichshare as many shape and size characteristics as possible, as well as asingle tool which can easily make the necessary cuts for all differentfemoral component sizes.

Another problem with known prior art artificial knee joints is that theycannot duplicate the large amount of flexion produced by a natural humanknee joint and still provide sufficient contact between the artificialfemur and the tibial component. Conventional artificial knee joints arelimited in further flexion because they typically cause the femur orstructure coupled to the femur to abut the tibia or structures coupledto the tibia to prevent further flexion. Accordingly, a need exists foran artificial knee joint which can provide as much flexion as possibleto more fully mimic a natural knee joint in performance.

Another problem with known prior art artificial knee joints is theirinability or difficulty in facilitating knee pivoting rotation in bothclockwise and counterclockwise directions. A natural knee joint iscapable of a small amount of pivoting rotation. Such pivoting rotationis particularly desirable when a person is walking along a curving path.

Some artificial knee joints, such as those taught by Hodge (U.S. Pat.No. 5,413,604) allow for pivoting rotation of the medial condyle aboutthe lateral condyle, but not rotation of the lateral condyle.Furthermore, other artificial knee joints, such as those taught byKaufman (U.S. Pat. No. 6,013,103) and Tuke (U.S. Pat. No. 5,219,362)describe pivoting rotation of the lateral condyle about the medialcondyle. Accordingly, a need exists for complete replication of functionof a natural knee joint, including pivoting rotation in both directions.

Another problem with known prior art artificial knee joints is the needfor the insert or other meniscal structure to exhibit a minimumthickness for suitable wear characteristics and duration, whileminimizing an amount of bone required to be removed from the proximalend of the tibia. Generally speaking, bone is removed from the proximalend of the natural tibia in an amount equaling a height of portions ofthe tibial component of the artificial knee joint which extend beyondthe proximal surface of the tibia after it has been prepared forreceiving the tibial component. Typically, regulatory authoritiesrecommend a six millimeter thickness on the insert or other meniscalwear structure, and structural portions of the tibial component needapproximately four millimeters for sufficient strength, a full tenmillimeters of bone must be removed from the proximal tibia to maintainproper ligament tension and maintain patient leg length. It is desirableto remove as little natural bone as possible, as natural bone isbeneficial in many respects and to be preferred over artificialstructures to the extent possible.

Prior art attempts have been made to nest the insert into the tibialcomponent somewhat, but only with joints that prevent twisting. See forinstance patent to Aubriot (U.S. Pat. No. 5,326,358) and Johnson (U.S.Pat. No. 4,568,348). Accordingly, a need exists for a tibial componentof an artificial knee joint which can maintain the regulatoryrecommended thickness of an insert or other wear structure whileminimizing a height of other portions of the tibial component of theartificial knee joint, and still allow twisting, to minimize the amountof required bone removal from the proximal end of the tibia.

SUMMARY OF THE INVENTION

With this invention, an artificial knee joint is provided which includesa femoral component and a tibial component that together satisfy theneeds and shortcomings of the prior art identified above. The jointincludes a femoral component surgically affixable to a distal end of afemur and a tibial component surgically affixable to a proximal end of atibia. An insert is also provided as a portion of the tibial componentwhich is removably attachable to the tibial component.

With this invention a jig is also provided to assist in making the cutsnecessary to form surfaces on the distal end of the femur appropriate tomate with facets on an internal box face of the femoral component. Thisjig includes slots or other guides for a cutting tool so that the jighelps the surgeon who is wielding the cutting tool to cut the properportions of the distal end of the femur away to provide the requiredsurfaces on the distal end of the femur.

The jig is provided to make appropriate cuts for multiple differentsizes of femoral components. In particular, slots or other cutting toolguide structures are provided which are the same for each size femoralcomponent to be surgically implanted, except for an anterior surface cutwhich is made at a variable distance from a posterior surface cut,depending on a size of the femoral component to be implanted. Otherslots or other structures within the jig are the same for other cuts tobe made to form the surfaces on the distal end of the femur for properfit with the selected femoral component.

Adjustability of the jig for cutting of the anterior surface is in oneembodiment provided by a plurality of separate anterior slots within thejig. In another embodiment, the jig is provided with an anterior slot ona moving portion of the jig that can slide relative to fixed portions ofthe jig to a desired position for making the necessary cut to form theanterior surface on the distal end of the femur.

The femoral component is generally in the form of a surfacing structureproviding a new wear surface on the distal end of the femur. As such itincludes a patellar flange portion adapted to be placed adjacent theanterior surface of the distal end of the femur and a medial condylarleg and a lateral condylar leg, both extending down from the patellarflange portion generally parallel to each other. The condylar legs curveposteriorly as they extend from the patellar flange portion.

A distal and posterior face of the femoral component is providedprimarily upon the medial condylar leg and lateral condylar leg and isadapted to abut with the insert of the tibial component of theartificial knee joint. The internal box face of the femoral componentincludes an anterior facet, a distal facet, a posterior facet, andpreferably a pair of diagonal facets at either side of the distal facet.The posterior facet is angled back toward a centerline of the femoralcomponent as the posterior facet extends away from the distal facet.Such a negative angle for the posterior facet of the internal boxsurface and corresponding forming of the posterior surface on the distalend of the femur, allows the distal face of the two condylar legs towrap around the posterior side of the distal end of the femursufficiently farther to allow an increase of contact and flexion inoperation of the knee joint when compared to prior art knee jointfemoral components.

The tibial component includes a substantially planar plate orientedsubstantially perpendicular to a shaft which is adapted to pass downinto a marrow of the tibia and substantially coaxial with a centerlineof the tibia. The insert is supported upon a proximal side of the plate.A dovetail rib extends in an anterior to posterior direction from theproximal surface of the plate. The insert includes a dovetail recesssized to be aligned with the dovetail rib on the plate so that theinsert can be slid onto the dovetail rib and held tightly to theproximal surface of the plate.

To minimize a thickness of the plate and an overall height of thecombination of the insert and the plate, the proximal surface of theplate includes depressions therein and a distal surface of the insertincludes lobes therein that drop down into the depressions in theproximal surface of the plate. In this way, a maximum thickness of theinsert is maintained, especially beneath wells in a proximal surface ofthe insert, without adding height to the overall insert and plate of thetibial component.

Two wells in the proximal surface of the insert have a curvaturematching a curvature of the condylar legs of the femoral component.Thus, the condylar legs of the femoral component can reside within thesegenerally spherical wells in the insert and the joint can experienceflexion while maintaining surface contact between the wells of theinsert and the condylar legs of the femoral component.

The wells have valleys that extend arcuately and mostly in an anteriordirection away from low points of the wells. These valleys are of lesserdepth in a distal direction as the valleys extend anteriorly away fromlow points of the wells. The valleys curve about a center point axisaligned with the low point of the other of the pair of wells. Side wallsof the valleys are appropriately gradual so that cross-sections of thevalleys perpendicular to centerlines of the valleys contain a curvaturesimilar to that of the condylar legs of the femoral component. In thisway, one of the condylar legs can remain at a low point within one ofthe wells while the other condylar leg can rotate along a valley of oneof the wells away from the low point and moving slightly upwardly in aproximal direction. As the elevation of the valleys increase, tension onligaments and muscles of the knee joint tighten to resist furtherpivoting rotation of the knee joint. Gravity loads tend to encourage thecondylar legs back to the low points of the wells, as well as forcesapplied by the ligaments and muscles themselves. Such pivoting rotationcan occur in either direction with one of the condylar legs remaining ina low point of one of the wells while the other condylar leg can movearcuately within its well. In this way, a small amount of knee pivotingrotation action is provided by the artificial knee joint of thisinvention, mimicking performance of a natural knee joint being replaced.

OBJECTS OF THE INVENTION

Accordingly, a primary object of the present invention is to provide anartificial knee joint which mimics as closely as possible the functionof a natural knee joint.

Another object of the present invention is to provide an artificial kneejoint which is easy for a surgeon to size and install properly.

Another object of the present invention is to provide a method andsystem for preparing a distal end of a femur for receipt of a femoralcomponent of an artificial knee joint which is easy to perform andsimilar for many different sizes of artificial knee joint components.

Another object of the present invention is to provide an artificial kneejoint sizing system which has multiple different size components thereinbut which maintain similar size for many portions thereof to simplifythe forming of cuts necessary to shape the distal end of the femur.

Another object of the present invention is to provide a single tool forshaping a distal end of the femur to receive a femoral component of anartificial knee joint which can properly shape the distal end of thefemur for a variety of different sizes of femoral components.

Another object of the present invention is to provide an artificial kneejoint which requires a minimal amount of bone removal from the proximalend of a tibia for receipt of a tibial component of the artificial kneejoint.

Another object of the present invention is to provide an artificial kneejoint which facilitates pivoting rotation in both a clockwise andcounterclockwise direction.

Another object of the present invention is to provide an artificial kneejoint which includes many portions thereof which are symmetrical andusable for either a left or right knee.

Another object of the present invention is to provide an artificial kneejoint which provides a greater amount of contact between condyles andincrease flexion within the artificial knee joint.

Another object of the present invention is to provide an artificial kneejoint which includes a set of femoral components of different sizes fordifferent sized femurs, with each of the components in the set havingmany surfaces which share a common size and shape, to simplify thedifferent cuts required on the distal end of the femur for receipt ofthe femoral component thereon.

Another object of the present invention is to provide an artificial kneejoint with a tibial insert for an artificial knee joint which is formedof a meniscus material that is available for wear that exhibits a lowprofile such that a minimum amount of natural tibia bone is required tobe removed.

Other further objects of the present invention will become apparent froma careful reading of the included drawing figures, the claims anddetailed description of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side elevation view of a distal end of a femur before cutsare made thereto to form surfaces on the distal end of the femur forreceipt of the femoral component of the artificial knee joint, and withcut lines to be made shown in broken lines thereon.

FIG. 2 is a side elevation view similar to that which is shown in FIG.1, but after making a first cut to the femur to form the distal surfaceof the femur, and after attachment of a fixed jig to the distal surfacefor guiding of cutting tools for the making of other cuts to form othersurfaces on the distal end of the femur.

FIGS. 3 and 4 are perspective views of an adjustable jig attachable tothe distal surface of the femur similar to the fixed jig of FIG. 2, butwhich adjustable jig features an adjustable portion for moving one ofthe slots to different distances adjustably spaced from other slotswithin fixed portions of the jig.

FIG. 5 is a side elevation view similar to that which is shown in FIG.2, but illustrating use of the adjustable jig of FIGS. 3 and 4 thereon.

FIG. 6 is a perspective view of the distal end of the femur with afemoral component of the artificial knee joint exploded therefrom, andillustrating how the femoral component is oriented and configured to fitupon the distal end of the femur.

FIG. 7 is a side elevation view of the distal end of the femur includinga femoral component attached thereto.

FIG. 8 is a perspective view of the femoral component of FIGS. 6 and 7.

FIG. 9 is a top plan view of that which is shown in FIG. 8.

FIG. 10 is a front elevation view of that which is shown in FIG. 8.

FIG. 11 is a rear sectional view of that which is shown in FIG. 8.

FIG. 12 is a side elevation view of that which is shown in FIG. 8, andillustrating in broken lines how two other femoral components of largerand smaller sizes share common surfaces with each other, except for ananterior facet and portions of a distal face of the femoral component toallow for simple size adjustability. This view also shows the femurs ofdifferent sizes matching those of the femoral components.

FIG. 13 is a side elevation view of that which is shown in FIG. 12without the femurs shown and depicting nine sizes of femoral componentsand how they relate together.

FIG. 14 is an exploded parts view of a tibial component of theartificial knee joint of this invention showing an insert portion of thetibial component exploded away from a plate and shaft portion of thetibial component, and exploded from a proximal end of a tibia.

FIG. 15 is a side elevation view of the tibial component shown in placeupon the proximal end of the tibia.

FIG. 16 is an exploded parts view of the entire artificial knee jointshown in perspective and from below.

FIG. 17 is a perspective view of the completed artificial knee joint inextension and with the femur and tibia brought together.

FIG. 18 is a sectional side elevation view of that which is shown inFIG. 17.

FIG. 19 is a side elevation view of that which is shown in FIG. 17, andwith a knee joint in a state of partial flexion.

FIG. 20 is a side elevation view similar to FIG. 19, but showing fullflexion of the knee joint.

FIGS. 21 and 22 are perspective views similar to that which is shown inFIG. 17, but illustrating pivoting rotation of the knee joint in both aclockwise and counterclockwise direction.

FIG. 23 is a top plan view of the insert of the tibial component of thisinvention.

FIG. 24 is a perspective view of the plate and shaft of the tibialcomponent of this invention.

FIG. 25 is a side elevation view of the tibial component showing theinsert portion in the process of being slid onto the plate.

FIG. 26 is a perspective view similar to that which is shown in FIG. 25but after the insert has been almost fully attached to the plate of thetibial component.

FIG. 27 is a perspective view similar to that which is shown in FIG. 26,but after the insert has been completely attached to the plate of thetibial component.

FIG. 28 is a full sectional elevation view of the tibial componentincluding the insert portion and the plate and shaft portion, with theinsert portion exploded away from other portions of the tibial componentto most clearly show complementally formed contours thereof.

FIG. 29 is a perspective view of an alternative tibial component with anaugment removably attachable thereto and shown exploded away from thetibial component and with a second position for the augment shown inbroken lines.

FIG. 30 is a perspective view of the alternative tibial component ofFIG. 29 with the augment attached to the tibial component.

FIG. 31 is a full sectional view of the alternative tibial component andaugment taken along line 31-31 of FIG. 30.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to the drawings, wherein like reference numerals representlike parts throughout the various drawing figures, reference numeral 10is directed to an artificial knee joint for replacing a natural kneejoint between a femur F and a tibia T. The invention includes a femoralcomponent 20 and a tibial component 40, as well as tools 2, 12 forforming a distal end of the femur F to receive the femoral component 20.The invention also includes methods for preparing the distal end of thefemur to receive an appropriately sized femoral component.

In essence, and with particular reference to FIGS. 15 and 16, the basicdetails of the artificial knee joint 10 are described, according to apreferred embodiment. The joint 10 includes the femoral component 20adapted to be coupled to an appropriately shaped distal end of the femurF. The joint 10 also includes a tibial component 40. The tibialcomponent 40 primarily includes a shaft 42 for insertion into theproximal end of the tibial T and a plate 50 of generally planar formperpendicular to the shaft 42. An insert 70 provides a removable portionof the tibial component 40 which attaches to the plate 50. This insert70 cooperates with a dovetail rib 60 on the plate 50 to secure theinsert 70 tightly to the plate 50. The insert 70 can then act somewhatas a meniscal component within the joint 10 for interfacing with thefemoral component 20 in an articulating fashion during operation of thejoint 10 (FIGS. 18-20).

More specifically, and with particular reference to FIGS. 1-5, detailsof jigs 2, 12 for use in forming surfaces of the distal end of the femurF to receive the femoral component 20, are described according to apreferred embodiment. Before using either of the jigs 2, 12, a cut C₁ ismade to the distal end of the femur (FIG. 1). This cut is typicallyapproximately perpendicular to the centerline L of the femur F, but mostpreferably slightly angled, as shown in FIG. 1. The fixed jig 2 providesone form of tool for assisting a surgeon in properly forming surfaces onthe distal end of the femur F to receive the femoral component 20. Thefixed jig 2 is generally in the form of a thick rigid structure whichhas an abutting face 4 which is caused to abut a distal surface of thefemur F formed by cut line C₁ (FIGS. 1 and 2). Pins or pegs 3 provideone form of means to temporarily secure the fixed jig 2 to the distalsurface of the femur F.

The fixed jig 2 includes a face 5 opposite the abutting surface 4. Slotspass from the face 5 to the abutting surface 4 for guiding of a cuttingtool through the fixed jig 2, then into bone of the femur F to form thesurfaces required on the distal end of the femur F to receive thefemoral component 20. In particular, a posterior slot 6 is providedpassing from the face 5 through to the abutting surface 4. Thisposterior slot 6 is utilized to form cut C₂ (FIGS. 1 and 2). Diagonalslots 7, 9 are separately utilized to form cuts C₃ and C₄.

The fixed jig 2 also includes an anterior slot array 8 aligned with cutlines C₅-C₁₃. In this embodiment nine separate anterior slots areprovided within the slot array 8. Each separate slot corresponds withone particular size for the femoral component 20 (FIG. 12). The surgeonmakes a determination as to which femoral component 20 would best beutilized with the patient. The surgeon then makes one cut through one ofthe anterior slots in the anterior slot array 8 to form the surfacecorresponding with cut C₅ (FIG. 1) or one of the other cut lines C₆-C₁₃(FIG. 2) to form the anterior surface of the distal end of the femur Fas desired to fit with the femoral component 20 that has been selected.

An adjustable jig 12 provides an alternative to the fixed jig 2. Theadjustable jig 12 (FIGS. 3-5) is generally similar to the fixed jig 2except where particularly described herein. An abutting surface 14 isthus provided for temporary attachment adjacent to the distal end of thefemur F formed by cut line C₁ (FIG. 1). Once the adjustable jig 12 isattached to the distal end of the femur F, a guide 13 is utilized whichslides (along arrow A of FIG. 5) relative to other portions of theadjustable jig 12 that are fixed to the femur F. When the guide 13 istouching the femur F, an adjustable slot 16 is positioned where desiredfor forming of a cut to form the anterior surface of the femur F.

This guide 13 is coupled to a structure in which the adjustable slot 16is formed, along with a mast 17. The mast 17 is adapted to slide withina groove 18 formed in fixed portions of the adjustable jig 12. Across-sectional contour of the mast 17 and groove 18 are preferablyselected to prevent rotation of the mast 17 within the groove 18, suchas a “cross” form (FIG. 3). Thus, the guide 13 and adjusting slot 16 canslide relative to other slots within the adjustable jig 12 to place theadjustable slot 16 where desired to form the cut associated with theanterior surface for the distal end of the femur F.

Most preferably, the face 15 of the adjustable jig 12 includes a setline 19 thereon and the mast 17 includes a series of numbers andassociated graduation marks thereon. These indicia and graduation markscould be placed on the face 15 with the set line 19 formed on the mast17 if desired. When the guide 13 abuts the femur F (FIG. 5) a user cansee which graduation adjacent which indicia is aligned with the set line19 (FIG. 4). This indicia, such as a number or letter, corresponds withthe size of femoral component (FIG. 12) that will properly fit upon thedistal end of the femur F after making cuts through the various slots ofthe adjustable jig 12.

Utilizing one of the jigs 2, 12 of this invention, each of the surfacesof the distal end of the femur are formed to have a similar size, shapeand relative orientation to other surfaces on the distal end of thefemur, with the exception of the anterior surface. This anterior surfacemaintains the same orientation relative to other surfaces on the distalend of the femur, but exhibits a variable distance away from theposterior surface of the distal end of the femur. Thus, each femoralcomponent 20 within a set of femoral components 20 of different sizes(FIG. 12) can be similar in size and shape, except for portions whichare to be located adjacent the anterior surface of the distal end of thefemur. Such anterior portions of the femoral component 20 are eachslightly modified for different sizes within the set of femoralcomponents. To achieve this similarity between femoral components ofdifferent sizes, one of the diagonal cuts exhibits variable length, withthis anterior diagonal cut being almost non-existent for the smallestfemur F, and largest to accommodate the largest femurs F.

In addition, the femoral component 20, while it could be made genericand suitable for use on either a left or right knee, is most preferablyoptimized to be slightly asymmetrical to be provided either on a leftknee or a right knee implantation site. Thus, overall a surgeon needonly have one jig, one cutting tool for use with the jig and one set offemoral components associated with the left or right knee that isreceiving the artificial knee joint. Simplicity and freedom frompotential error results from such a simplified system.

With particular reference to FIGS. 6-17, details of the femoralcomponent 20 of the artificial knee joint 10 are described, according toa preferred embodiment. These details are described with regard to afemoral component 20 of midsize (FIG. 12), with details of other femoralcomponents 20 within a set of different sizes of femoral components 20being similar, except for size adjustability as depicted in FIG. 12.

The femoral component 20 generally includes a medial condylar leg 22 anda lateral condylar leg 24 which each extent from a patellar flangeportion 26. Legs 22, 24 exhibit a curvature which allow them to wraparound the distal end of the femur F from the anterior surface to theposterior surface and over the distal surface of the femur F. A distalface 28 of the femoral component 20 is a generally curving surfaceoptimized to abut and articulate against the insert 70 of the tibialcomponent 40 described in detail below. Each condylar leg 22, 24 has aseparate (same) curvature on the distal face 28 which is preferablysubstantially spherical, and most importantly has a curvature whichmatches that of the wells 77, 78 on the proximal surface 76 of theinsert 70, described in detail below.

An internal box face 30 defines that portion of the femoral component 20which abuts against the distal end of the femur F. This internal boxface 30 is divided into separate facets to which an adhesion medium canengage, or other fastening structures can be connected. The internal boxface 30 includes a distal facet 32 which is close to perpendicular to acenterline of the femoral component 20, with a centerline of the femoralcomponent 20 defined as a line aligned with a centerline of the femur Fwhen the femoral component 20 is attached to the distal end of the femurF. However, the distal facet 32 preferably extends slightly furtherdistally on a side of the distal facet 32 closest to the posteriordiagonal facet 38. The distal facet 32 can support an axial structurewhich can penetrate into the femur F, or other attachment structures canbe provided to extend generally proximally into the femur F. The distalfacet 32 preferably maintains its size and shape for all sizes offemoral components 20.

The distal facet 32 is preferably substantially planar, but could have adiffering contour provided that the distal surface of the distal end ofthe femur F is similarly formed. Because planar surfaces are most easilyformed on the distal end of the femur F, the internal box face 30 of thefemoral component 20 is similarly formed with planar facets such as thedistal facet 32.

An anterior face 34 defines a portion of the internal box face 30 of thefemoral component 20 adapted to abut against the anterior surface of thedistal end of the femur F. A posterior facet 35 is similarly adapted toabut the posterior surface of the distal end of the femur F. An anteriordiagonal facet 36 extends diagonally between the distal facet 32 and theanterior facet 34. This anterior diagonal facet 36 is of varying sizedepending on which femoral component 20 size is involved. A posteriordiagonal facet 38 extends between the posterior facet 35 and the distalfacet 32.

Each of these facets 32, 34, 35, 36, 38 are preferably each planar andjoined to adjacent facets 32, 34, 35, 36, 38 along transition lineswhich are linear in form and extend laterally an entire width of theinternal box face 30 of the femoral component 20 (FIG. 8). Mostpreferably, these transition lines include ribs thereon with otherportions of the facets 32, 34, 35, 36, 38 away from these transitionlines recessed slightly. Side edges of the internal box face 30 can alsobe raised slightly. Such ribs are depicted in FIGS. 6, 8-11 and 17, butcould have a variety of different configurations or could be omittedaltogether. Recesses between the ribs provide a region for adhesive orbone in-growth medial to help adhere the femoral component 20 to thefemur F.

Importantly, the posterior facet 35 has a negative angle α (FIGS. 2 and19) relative to a centerline of the femoral component 20 and acenterline of the femur F when attached to the femur F. As best depictedin FIG. 18, this negative angle α is most preferably approximately 3°,but could be increased or decreased to optimize the design. Prior artfemoral components of artificial knee joints are not known to have sucha negative angle. By providing such a negative angle, a greater amountof flexion and contact can be obtained (along arrow B of FIG. 18)between the tibia T and femur F.

Cut line C₂ associated with posterior slot 6 in the fixed jig 2 (FIG. 2)provides the internal box surface of the distal end of the femur F witha negative angle relative to a centerline of the femur F whichcorresponds with the negative angle of the posterior facet 35 relativeto a centerline of the femoral component 20 (FIG. 18).

Note that this posterior facet 35 is in fact a pair of separate facetswith each facet on one of the condylar legs 22, 24. Also, the posteriordiagonal facet 38 is actually split between the two condylar legs 22, 24and the distal facet 32 extends partially onto each of the legs 22, 24.As these split facets 32, 35, 38 are coplanar, they are often referredto as a single plane and a single facet for simplification.

The anterior diagonal facet 36 maintains a common position for each sizeof femoral component 20 (FIG. 12. However, this facet 36 varies inlength to accommodate anterior facets 34 of different positions for thedifferent femoral component sizes. For a smallest size, this anteriordiagonal facet 36 is reduced to zero or near zero length so that theanterior facet is directly or almost directly adjacent the distal facet32. Other facets preferably maintain their size and relative orientationfor the different sized femoral components 20.

With particular reference to FIGS. 13-26, details of the tibialcomponent 40 are described, according to a preferred embodiment. Thetibial component 40 is preferably formed as a rigid construct from highstrength material such as titanium or cobalt chrome. The tibialcomponent includes a shaft 42 of elongate form adapted to be alignedwith a centerline of the tibia T and to be driven down into a marrowspace within the tibia T. This shaft 42 extends down from a plate 50which is generally planar and oriented generally perpendicular to theshaft 42. The plate 50 is adapted to abut the proximal surface of thetibia T. Gussets 44 are formed on sides of the shaft 42 and generallybecome thicker as the gussets 44 extend proximally toward the plate 50.These gussets 44 help to give additional strength to the plate 50 and tothe shaft 42, and also to further assist the shaft 42 and tibialcomponent 40 overall in being securely affixed to the tibia T.Furthermore, prongs 46 preferably extend distally from the plate 50 tofurther engage the proximal end of the tibia T.

The plate 50 is generally oval shaped and is perhaps best seen in FIG.22. The plate 50 includes a pair of spherical depressions 52 on eitherside of a dovetail rib 60 passing medially between the sphericaldepressions 52. The spherical depressions 52 need not necessarily bespherical, but could have some other contour. These depressions 52extend distally down into the plate 50 and help to make the tibialcomponent 40 exhibit an overall lesser distal height to minimize anamount of bone required to be removed from the tibia T.

The plate 50 includes a posterior wall 54 extending up from a posterioredge of the plate 50. An anterior tab 56 also extends up from the plate50 near a lateral midpoint of the anterior edge of the plate 50. A tooth58 extends posteriorly from the anterior tab 56. The tab 56 helps tohold the insert 70 onto the plate 50, as described in detail below. Mostpreferably the posterior wall 54 exhibits an overhang that extendsanteriorly to some extent. This overhang helps the posterior wall 54 tohold the insert 70 securely adjacent the plate 50, as described indetail below.

The dovetail rib 60 extends proximally up from a midportion of the plate50. This dovetail rib 60 is elongate in form extending from an anteriorend 62 to a posterior end 64. The anterior end 62 stops short of theanterior tab 56, so that a gap exists between the anterior tab 56 andthe anterior end 62 of the dovetail rib 60. The posterior end 64 of thedovetail rib 60 is preferably joined with the posterior wall 54extending up from the proximal surface of the plate 50.

The dovetail rib 60 includes a pair of substantially parallel side walls66 adjacent to the proximal surface of the plate 50 and forming a lowerportion of the dovetail rib 60 joining the dovetail rib 60 to the plate50 (FIGS. 23 and 26). A top wall 65 defines a portion of the dovetailrib 60 extending most proximally from the plate 50. The top wall 65exhibits a taper in a distal and posterior direction from the anteriorend 62 toward the posterior end 64.

Beveled walls 68 extend up from the side walls 66 to the top wall 65.These beveled walls 68 provide the dovetail rib 60 with its dovetailcross-section. The beveled walls 68 preferably maintain their form fromthe anterior end 62 to the posterior end 64. The side walls 66preferably taper in height from a greatest height adjacent the anteriorend 62 to a least proximal height adjacent the posterior end 64, wheremost preferably the side walls 66 merge into the proximal surface of theplate 50, so that adjacent the posterior end 64, the dovetail rib 60 isformed of only the beveled wall 68, without the side walls 66. Thistapering of the dovetail rib 60 causes a wedging action with thedovetail recess 74 of the insert 70 when the insert 70 is slid onto thedovetail rib 60 (along arrow J of FIG. 25).

Most preferably, the entire dovetail rib 60, anterior tab 56, posteriorwall 54, plate 50, shaft 42 and prongs 46 are formed together as aunitary monolithic mass of a common material. Such forming could be bymolding, machining or some combination of procedures. As an alternative,various separate parts of the tibial component 40 could be attachedtogether, such as by welding or other bonding, or through utilization ofappropriate biocompatible fasteners.

The tibial component 40 also can be considered to include the insert 70as a separately attachable portion thereof. Within the artificial kneejoint 10, the insert 70 moves along with the plate 50 and shaft 40 as asingle structure. However, the insert 70 can be removably attached fromand to other portions of the tibial component 40. Also, the insert 70 istypically formed of a more resilient material than that forming otherportions of the tibial component 40, and particularly the plate 50 andshaft 42. For instance, the insert 70 could be formed of a biocompatiblepolymeric hydrocarbon material which has some degree of resilience andflexibility to best accommodate loads associated with the femoralcomponent 20 pressing down on the insert 70 in a distal direction.

The insert 70 is itself a monolithic structure formed such as by moldingor machining to have the contours shown in FIGS. 13-21 and 23-26. Theinsert 70 includes a distal surface 72 adapted to abut the plate 50.Spherical lobes 73 extend down from the distal surface 72 to residewithin the spherical depressions 52 in the plate 50. These sphericallobes 73 could be a different shape, particularly if the depressions 52are a shape different than spherical. Also, while the lobes 73preferably fill the depressions 52, they could be smaller than or adifferent shape than the depressions 52.

The distal surface 72 of the insert 70 also includes a dovetail recess74 therein. This dovetail recess 74 is interposed between engagementbars 75. The dovetail recess 74 has a contour similar to that of thedovetail rib 60. Thus, the insert 70 can have its dovetail recess 74slid onto the dovetail rib 60 (arrow J of FIG. 23) to attach the insert70 to the plate 50.

The insert 70 includes a proximal surface 76 opposite the distal surface72. The proximal surface 76 is adapted to support the femoral component20 or other femoral structures thereon. For instance, it is conceivablethat the femur F might not be modified, but impact directly upon theproximal surface 76 of the insert 70, or that some other form ofinterface besides the femoral component 70 might be utilized. Theproximal surface 76 is perhaps best seen in FIG. 21. A left well 77 andright well 78 extend distally down into the proximal surface 76. Arecess 79 is formed on an anterior portion of the insert 70. This recess79 is sized to receive the tab 56 and tooth 58 therein to lock theinsert 70 to the plate 50 most securely.

The wells 77, 78 exhibit a particular contour to allow both flexion ofthe femoral component 20 relative to the tibial component 40, and also adegree of pivoting rotation (about arrows D and E of FIGS. 19 and 20) inboth a clockwise and counterclockwise direction. In particular, thewells 77, 78 include low points 80, 81 that define most distal portionsof the wells 77, 78. Side walls of the wells 77, 78 near these lowpoints 80, 81 are preferably substantially spherical in form matching aradius of curvature of the condylar legs 22, 24 of the femoral component20. If these condylar legs 22, 24 exhibit a contour other thanspherical, most preferably surfaces of the wells 77, 78 adjacent the lowpoints 80, 81 would be appropriately modified to match such curvature.

By matching this curvature, surface contact is provided between thewells 77, 78 and the condylar legs 22, 24. Thus, both gravity forces andforces applied by muscles and tendons will tend to cause the condylarlegs 22, 24 to remain within the wells 77, 78 adjacent the low points80, 81 thereof. Such positioning will be maintained during flexion(rotation along arrow B of FIG. 18). However, if pivoting rotating loadsare applied (such as along arrows D and E of FIGS. 19 and 20) suchpivoting rotation is accommodated.

In particular, if the medial condylar leg 22 is located within the rightwell 78 and the lateral condylar leg 24 is located within the left well77, before pivoting rotation action, the medial condylar leg 22 will bealigned with the low point 81 and the lateral condylar leg 24 will bealigned with the low point 80. For pivoting rotation in a clockwisedirection, the medial condylar leg 22 will remain at the low point 81.However, the lateral condylar leg 24 will rotate along arrow E (FIGS. 19and 21) along a left valley 82 within the left well 77 in a generallyanterior direction, but following an arc maintaining a constant distancefrom the low point 81 of the right well 78, depicted by arrow H (FIG.21).

Alternatively, if pivoting rotation is required in a counterclockwisedirection, the lateral condylar leg 24 will remain within the low point80 of the left well 77 and the medial condylar leg 22 within the rightwell 78 will move out of the low point 81 and along the right valley 83along arrow D (FIGS. 20 and 21). This right valley 83 is defined by aconstant distance away from the low point 80 of the left well 77depicted by arrow G (FIG. 21).

The valleys 82, 83 slope proximally away from the low points 80, 81slightly. Thus, as such pivoting rotation action occurs, the condylarlegs 22, 24 are moving anteriorly and proximally along the valleys 82,83. This adds tension to the ligaments and muscles around the knee joint10 and require work against gravity. Preferably, the slope of thevalleys 82, 83 away from the low points 80, 81 rather significantlyincreases in slope near an end point of the valleys 82, 83 most distantfrom the low points 80, 81. Thus, the legs 22, 24 would need to moveproximally at a significantly more rapid rate as a greater amount ofpivoting rotation is encountered. Knee ligaments and muscles, as well asgravity resist such further pivoting rotation, such that the knee hasstability against excessive pivoting rotation.

While the condylar legs 22, 24 and the wells 77, 78 enjoy surfacecontact over at least portions thereof before such pivoting rotationoccurs, such surface contact is maintained even during pivoting rotationfor the one condylar leg 22, 24 which remains stationary within the lowpoint 80, 81. For the other condylar leg 24, 22, that is moving along avalley 82, 83 within one of the wells 77, 78, contours of side walls ofthe wells 77, 78 on either side of the valleys 82, 83 are configuredwith a cross-section perpendicular to a centerline of the valleys 82, 83which matches a cross-section of the condylar legs 22, 24. Thus, contactis maintained for the legs 22, 24 moving within the valley 82, 83 awayfrom the low point 80, 81. Thus, point loads are avoided even duringsuch pivoting rotation motion. By distributing loads and avoiding pointloading, but rather either line loading or surface loading, a rate ofwear and stress upon the insert 70 and the femoral component 20 isminimized.

Additionally, because the wells 77, 78 extend down into the proximalsurface 76 of the insert 70, and because regulatory agencies typicallyrecommend a minimum amount of wear height within the insert 70 or othermeniscal structure, having a flat distal surface 72 on the insert 70would require the insert 70 to exhibit a greater height similar to adepth of the wells 77, 78 than if the wells were not there. Forinstance, it is recommended that if a minimum of six millimeters must bemaintained within the insert 70, upon implantation, and if the wells 77,78 have three millimeters of distal depth, the proximal surface 76 ofthe insert 70 must be at least nine millimeters away from the distalsurface 72.

By providing spherical lobes 73 on the distal surface 72 of the insert70, such as three millimeters thick, and similar depressions 52 in theplate 50, the required thickness for the insert 70 can be maintained(i.e. six millimeters) without requiring a perimeter distance betweenthe distal surface 72 and proximal surface 76 to be increased. Rather,thickness is maintained while shortening an overall height of the tibialcomponent 40 of the joint 10.

Because the depressions 52 in the plate 50 reduce the strength of theplate 50 somewhat, the gussets 44 are provided to maintain sufficientplate 50 strength. In particular, the gussets 44 preferably aregenerally triangularly shaped planar structures oriented insubstantially vertical planes radiating from the shaft 42. Preferably,four gussets 44 are provided with a widest portion of each gusset 44adjacent the underside of the plate 50 and narrowing down to the tip ofthe shaft 42 most distant from the plate 50. Also, prongs 46 extend downsubstantially vertically from the underside of the plate 50 at locationsspaced from the shaft 42. Preferably, four such prongs 46 are providedwith a length of about a fourth that of the shaft 42. Overall, suchnesting of a portion of the insert 70 within a portion of the plate 50can provide up to a two or three millimeter reduction in the amount oftibial bone loss in implantation of the artificial knee joint 10according to this invention.

With particular reference to FIGS. 29-31, details of an alternativetibial component 140 and associated augment 170 are described. When anatural tibia T adjacent an artificial knee joint 10 has less than fullyadequate bone volume directly adjacent the tibial component, it isdesirable that at least a portion of the tibial component be augmentedin thickness to make up for the absence of desirable bone volume. Oftensuch tibial bone volume deficiency is limited to only a portion of thetibia T. With this invention, as shown in the embodiment of FIGS. 29-31,an augment 170 can be added to the alternative tibial component 140 onat least one half of the alternative tibial component 140 and a portionof the tibia T cut away to accommodate this augmented alternative tibialcomponent 140.

In particular, the alternative tibial component 140 is similar to thetibial component 40 of the preferred embodiment, described above, exceptthat the shaft 142 is depicted in this embodiment as tapering somewhatin diameter as it extends towards a tip, and is shown somewhatelongated. This shaft 142 variation is provided to illustrate thevariety of different configurations for the shaft 140 that are withinthe scope of this invention. Similarly, the gussets 144 have a slightlydifferent shape than that of the gussets 44 of the preferred embodimentdescribed above. The alternative tibial component 140 includes a plate150 similar in form and function to the plate 50 of the tibial component40 described above.

Uniquely, the alternative tibial component 140 (FIGS. 29-31) includesthreaded prongs 160 extending perpendicularly in a distal direction fromthe underside of the plate 150, and generally parallel with the shaft142. These threaded prongs 160 have a pointed tip 162 and threads 164 ona cylindrical side thereof. When the alternative tibial component 140 isnot required to be augmented with the augment 170, these threads 164 onthe threaded prongs 160 can help assist bone in-growth and secureattachment of the tibia T to the alternative tibial component 140. Ifthe alternative tibial component 140 requires augmentation, the augment170 can be utilized on either side of the alternative tibial component140, or two augments 170 can be provided, so that both sides of thealternative tibial component 140 are augmented in thickness.

The augment 170 preferably is a plate having a constant thicknessbetween a substantially planar top surface 172 and a substantiallyplanar bottom surface 174. A perimeter 176 extends between the topsurface 172 and bottom surface 174. This perimeter 176 follows a contourof the underside of the plate 150. Because the plate 150 is bilaterallysymmetrical, and because the top surface 172 and bottom surface 174 areboth planar, and oriented parallel to each other, and the entire augment170 is generally thin in form, it can be reversed to fit on either aleft or right side of the alternative tibial component 140, merely bereversing the top surface 172 or the bottom surface 174.

The augment 170 includes slots 178 therein which can be aligned with thegussets 144 to help to stabilize the augment 170 and securely hold theaugment 170 to the plate 150. Furthermore, the augment 170 preferablyincludes a pair of bores 175 aligning with two of the threaded prongs160. While the preferred embodiment shows two of these threaded prongs160, it is conceivable that the augment 170 could be attached with onlya single threaded prong 160 and the slots 178 and gussets 144 couldcoact together to prevent rotation of the augment 170 relative to theplate 150 about such a single prong 160.

The bores 175 preferably include steps 177 therein both at an upper andlower end of the bores 175. These steps 177 allow for recessing of nuts188 as described in detail below.

The nuts 188 preferably have a generally cylindrical form with athreaded bore 182 on an interior portion thereof and with a face 186 onone end forming a flange 184 having a slightly greater diameter thanother portions of the nut 180. This flange 184 has a diameter similar tothat of the bores 175 at the step 177. Other portions of each nut 180preferably have a diameter similar to that of the bores 175 spaced fromthe step 177. Each nut 180 can thus be recessed into the bore 175 withthe flange 184 within the step 177 for complete recessing of the nuts180.

A face 186 on each nut 180 preferably includes holes which can receive atorque applying tool so that the nuts 180 to be completely rotated intoposition. As an alternative to such holes, slits could be formed in theface 186, or other engagement structures could be provided on the face186 to facilitate rotation of the nuts 180, even as they are beingrecessed into the bores 175 of the augment 170. Once one or moreaugments 170 are attached to the alternative tibial component 140, theaugments 170 become part of the alternative tibial component 140 forimplantation within the knee joint 10.

Referring to FIG. 31, a gap can be seen between the augment 170 and theplate 150 of the alternative tibial component 140. The plate 150 has aperipheral lip extending downwardly and against which the augment 170comes into contact when the augment 170 is attached to the plate 150.Preferably, surfaces of the augment 170, including the surface 172 andthe surface 174 include a peripheral rib extending perpendicularly fromthe surface 172 and the surface 174. These peripheral ribs extendperpendicularly from the surface and inboard of the perimeter 176 by adistance similar to a width of the peripheral lip on the plate 150, sothat the peripheral rib is located inboard of the peripheral lip on theplate 150. This peripheral rib can thus help to keep the augment 170precisely aligned where desired relative to the alternative tibialcomponent 140. To further stabilize the augment 170, ribs having otherpatterns could also extend from the surfaces 172, 174 inboard of theperipheral rib to provide further contact between the augment 170 andthe plate 150 and still maintain reversibility for the augment 170. Oneparticular place for such ribs is surrounding the bores 175 to supportthe augment 170 at this attachment location.

This disclosure is provided to reveal a preferred embodiment of theinvention and a best mode for practicing the invention. Having thusdescribed the invention in this way, it should be apparent that variousdifferent modifications can be made to the preferred embodiment withoutdeparting from the scope and spirit of this invention disclosure. Whenstructures are identified as a means to perform a function, theidentification is intended to include all structures which can performthe function specified. When structures of this invention are identifiedas being coupled together, such language should be interpreted broadlyto include the structures being coupled directly together or coupledtogether through intervening structures. Such coupling could bepermanent or temporary and either in a rigid fashion or in a fashionwhich allows pivoting, sliding or other relative motion while stillproviding some form of attachment, unless specifically restricted.

What is claimed is:
 1. A tibial component for an artificial knee joint,comprising in combination: a shaft adapted to be located axially withina proximal end of a tibia; a plate fixed to said shaft and orientedprimarily within a plane substantially perpendicular to said shaft; aninsert adapted to be coupled to a proximal side of said plate oppositesaid shaft; said insert adapted to support femoral loads thereon; adovetail rib extending up from said plate; a dovetail recess in a distalsurface of said insert, said dovetail recess sized to receive saiddovetail rib therein; wherein said insert includes a proximal surfacehaving a pair of wells therein, each well adapted to receive a condylarstructure therein; wherein said wells each include a valley extendingarcuately away from a low point within each said well, each of saidvalleys tapering upward away from a respective one of said low points ofsaid wells with arcs each curving about a respective center point axisaligned with the low point of the other said well on said proximalsurface of said insert, said valleys adapted to maintain alignment forpassing of a condylar structure along one of said valleys while anothercondylar structure remains located within a low point of the other saidwell; wherein said low point within each well defines a most distalportion of each well, with said proximal surface extending proximally inevery direction away from each said well; and wherein said valleys eachexhibit a proximal slope away from said low point of each said well, assaid valleys extend anteriorly from said low point of each said well. 2.The tibial component of claim 1 wherein said dovetail recess is open ata posterior end of said dovetail recess corresponding with a posteriorend of the dovetail rib opposite an anterior end of the dovetail rib. 3.The jet component of claim 2 wherein said dovetail recess has ananterior end which stops short of an anterior side of said insert. 4.The tibial component of claim 3 wherein said dovetail rib has a lengthbetween an anterior end and a posterior end, said anterior end extendingfurther proximally from said plate than said posterior end of said rib,such that a proximal height of said dovetail rib above proximal side ofsaid plate tapers down from said anterior end of said rib to saidposterior end of said rib.
 5. The tibial component of claim 1 whereinsaid wells are symmetrical about a centerline between said wells, suchthat similar pivoting about each said condylar structure isaccommodated; and wherein said valleys taper proximally more graduallyas said valleys extend in an anterior direction away from said low pointthan said valleys taper proximally as said valleys extend in a posteriordirection, such that anterior rotation is accommodated more thanposterior rotation.
 6. The tibial component of claim 5 wherein saidinsert includes a distal surface opposite said proximal surface, saiddistal surface including lobes which extend distally from said distalsurface, said lobes being semi-spherical in form, said lobes extendingfrom said distal surface to an extent at least as great as a depth ofsaid wells, with one of said lobes beneath each of said wells, such thatmaterial thickness of said insert is maintained without requiring theentire distal surface to extend distally as far as said lobes.
 7. Atibial component for an artificial knee joint, comprising incombination: a shaft adapted to be located axially within a proximal endof a tibia; a plate coupled to said shaft and oriented primarily withina plane substantially perpendicular to said shaft; an insert adapted tobe coupled to a proximal side of said plate opposite said shaft; saidinsert adapted to support femoral loads thereon; a dovetail ribextending up from said plate; a dovetail recess in a distal surface ofsaid insert, said dovetail recess sized to receive said dovetail ribtherein; wherein said insert includes a proximal surface having a pairof wells therein, each well adapted to receive a condylar structuretherein; wherein said wells each include a valley extending arcuatelyaway from a low point within each said well, each of said valleystapering upward away from a respective one of said low points of saidwells with arcs each curving about a respective center point axisaligned with the low point of the other said well on said proximalsurface of said insert, said valleys adapted to maintain alignment forpassing of a condylar structure along one of said valleys while anothercondylar structure remains located within a low point of the other saidwell; wherein said low point within each well defines a most distalportion of each well, with said proximal surface extending proximally inevery direction away from each said well; and wherein said valleys eachexhibit a proximal slope away from said low point of each said well, assaid valleys extend anteriorly from said low point of each said well. 8.The tibial component of claim 7 wherein said dovetail recess is open ata posterior end of said dovetail recess corresponding with a posteriorend of the dovetail rib opposite an anterior end of the dovetail rib. 9.The tibial component of claim 8 wherein said dovetail recess has ananterior end which stops short of an anterior side of said insert. 10.The tibial component of claim 9 wherein said dovetail rib has a lengthbetween an anterior end and a posterior end, said anterior end extendingfurther proximally from said plate than said posterior end of said rib,such that a proximal height of said dovetail rib above proximal side ofsaid plate tapers down from said anterior end of said rib to saidposterior end of said rib.
 11. The tibial component of claim 7 whereinsaid wells are symmetrical about a centerline between said wells, suchthat similar pivoting about each said condylar structure isaccommodated; and wherein said valleys taper proximally more graduallyas said valleys extend in an anterior direction away from said low pointthat said valleys taper proximally as said valleys extend in a posteriordirection, such than anterior rotation is accommodated more thanposterior rotation.
 12. The tibial component of claim 11 wherein saidinsert includes a distal surface opposite said proximal surface, saiddistal surface including lobes which extend distally from said distalsurface, said lobes being substantially semi-spherical in form, saidlobes extending from said distal surface to an extent at least as greatas a depth of said wells, with one of said lobes beneath each of saidwells, such that material thickness of said insert is maintained withoutrequiring the entire distal surface to extend distally as far as saidlobes.
 13. A tibial component for an artificial knee joint, comprisingin combination: a shaft adapted to be located axially within a proximalend of a tibia; a plate fixed to said shaft and oriented primarilywithin a plane substantially perpendicular to said shaft; an insertadapted to be coupled to a proximal side of said plate opposite saidshaft; said insert adapted to support femoral loads thereon; a dovetailrib extending up from said plate, said dovetail rib having a lengthbetween an anterior end and a posterior end, said anterior end extendingfurther proximally from said plate than said posterior end of said rib,such that a proximal height of said dovetail rib above proximal side ofsaid plate tapers down from said anterior end of said rib to saidposterior end of said rib; a dovetail recess in a distal surface of saidinsert, said dovetail recess sized to receive said dovetail rib therein;wherein said proximal side of said plate includes depressions therein,one on either side of said dovetail rib, and said insert includes adistal surface having lobes thereon, said lobes sized to fit within saiddepressions in said plate; wherein said insert includes a proximalsurface having a pair of symmetrical wells therein, each well adapted toreceive a condylar structure therein wherein said wells each include avalley extending arcuately away from a low point within each said well,each of said valleys tapering upward away from a respective one of saidlow points of said wells with arcs each curving about a respectivecenter point axis aligned with the low point of the other said well onsaid proximal surface of said insert, said valleys adapted to maintainalignment for passing of a condylar structure along one of said valleyswhile another condylar structure remains located within a low point ofthe other said well; wherein said low point within each well defines amost distal portion of each well, with said proximal surface extendingproximally in every direction away from each said well; and wherein saidvalleys each exhibit a proximal slope away from said low point of eachsaid well, as said valleys extend anteriorly from said low point of eachsaid well.
 14. The tibial component of claim 13 wherein said dovetailrib includes two opposing substantially parallel side walls extendingproximally from said plate and forming a lower portion of said dovetailrib adjacent said proximal surface of said plate.
 15. The tibialcomponent of claim 14 wherein said dovetail rib includes beveled wallson opposite sides of said dovetail rib above said side walls andextending up to a top wall of said dovetail rib, said beveled wallshaving a constant distance between said top wall and portions of saidbeveled walls adjacent said side walls, this constant distancemaintained from said anterior end to said posterior end and said sidewall tapering from a greater height up from said plate at said anteriorend to a lesser height up from said plate at said posterior end.
 16. Thetibial component of claim 15 wherein said dovetail rib merges into aposterior wall extending laterally generally perpendicular to saiddovetail rib, said insert adapted to abut said posterior wall when saiddovetail recess of said insert has been fully slid onto said dovetailrib of said plate.
 17. The tibial component of claim 16 wherein ananterior clip extends up from said proximal surface of said plate at alocation spaced from said anterior end of said dovetail rib, saidanterior clip having a tooth, said insert including a recess thereinadapted to receive said anterior clip therein when said insert has beenfully located upon said plate with said dovetail rib within saiddovetail recess.
 18. The tibial component of claim 13 wherein ananterior clip extends up from said proximal surface of said plate at alocation spaced from said anterior end of said dovetail rib, saidanterior clip having a tooth, said insert including a recess thereinadapted to receive said anterior clip therein when said insert has beenfully located upon said plate with said dovetail rib within saiddovetail recess.